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Revision as of 09:47, 13 March 2007

This page describes my proposal for development of new standard low-level I/O library -- Bulatz 09:29, 13 March 2007 (UTC)

The existing GHC I/O library (based on using Handles) is very feature-rich, but it cannot be extended any more. The reason is that this library has non-modular design where all features are closely coupled with each other and GHC RTS. But we need to further extend it, adding the following facilities:

  • More models for async i/o (support for kqueue,epoll,AIO)
  • Unicode filenames on windows and unix
  • Using ByteString/UTF8String/UTF16String for filenames
  • Various encodings (UTF8,UTF16...) for text files
  • Files>4gb on windows
  • Memory-mapped files
  • ByteString i/o
  • Binary i/o and binary serialization

Although additional libraries ([1]-[4]) solves almost every problem mentioned here, they are not coupled together - you can't use async i/o from network-alt with ByteString I/O from FPS and Char encoding routines from Streams. I don't even say that most of this features are simply not available for other Haskell compilers.

On the other hand, there are alternative designs for implementation of higher-level features such as buffering and text encoding (at least, Streams vs SSC). Moreover, higher-level implementation greaty depends on language-extension features (such as MPTC+FD) whose support varies between haskell compilers. As a result, i propose to develop standard *low-level* I/O library that will hide details of interacion with OS but don't provide any higher-level interfaces to work with files - it would be a business for other libs.

So, what i propose to include in this lib:

0) Prerequisites: implementation in FPS or some other library common operations on ByteString/UTF8String/UTF16String and providing some Stringable class that provides type-independent interface to these operations:

class Stringable a where
  length :: a -> Int
  concat :: [a] -> a
instance Stringable String
instance Stringable ByteString
instance Stringable UTF8String
instance Stringable UTF16String